Two-Month administration of Methylphenidate improves olfactory sensitivity and suppresses appetite in individuals with obesity

Introduction: Olfaction contributes to feeding behaviour and is modulated by changes in dopamine levels. Methylphenidate (MPH) increases brain dopamine levels and has been shown to reduce appetite and promote weight loss in patients with attention deficit hyperactivity disorder. The objectives of this study were to test the effect of MPH on olfaction, appetite, energy intake and body weight on individuals with obesity. Methods: In a randomized, double-blind study, 12 participants (age 28.9±6.7 yrs) (BMI 36.1±4.5 kg/m2) were assigned to MPH (0.5mg/kg) (n=5) or Placebo (n=7) twice daily for 2 months. Appetite (Visual Analog Scale), odour threshold (Sniffin’ Sticks®), energy intake (food menu), and body weight (DEXA scan) were measured at day 1 and day 60. Results: MPH intake significantly increased odour threshold scores (6.3±1.4 vs. 9.4±2.1 and 7.9±2.3 vs. 7.8±1.9, respectively; p=0.029) vs. Placebo. There was a significantly greater suppression of appetite sensations (desire to eat (p=0.001), hunger (p=0.008), and prospective food consumption (p=0.003)) and an increase in fullness (p=0.028) over time in the MPH vs. Placebo. Conclusions: MPH suppressed appetite and improved olfactory sensitivity in individuals with obesity. These data provide novel findings on the favourable effects of MPH on appetite and weight regulation in individuals living with obesity.

Variant A of the Deformed Wings Virus Alters the Olfactory Sensitivity and the Expression of Odorant Binding Proteins on Antennas of Apis mellifera

Insects have a highly sensitive sense of smell, allowing them to perform complex behaviors, such as foraging and peer recognition. Their sense of smell is based on the recognition of ligands and is mainly coordinated by odorant-binding proteins (OBPs). In Apis mellifera, behavior can be affected by different pathogens, including deformed wing virus (DWV) and its variants. In particular, it has been shown that variant A of DWV (DWV-A) is capable of altering the ultra-cellular structure associated with olfactory activity. In this study was evaluated olfactory sensitivity and the expression of OBP genes in honey bees inoculated with DWV-A. Electroantennographic analyses (EAG) were carried out to determine the olfactory sensitivity to the essential oils Eucalyptus globulus and Mentha piperita. The expression of nine antenna-specific OBP genes and DWV-A load in inoculated bees was also quantified by qPCR. We observed an inverse relationship between viral load and olfactory sensitivity and the expression of some OBP proteins. Thus, high viral loads reduced olfactory sensitivity to essential oils and the gene expression of the OBP2, OBP5, OBP11, and OBP12 proteins on the antennas of middle- and forager-age bees. These results suggest that DWV-A could have negative effects on the processes of aroma perception by worker bees, affecting their performance in tasks carried out in and outside the colony.

Suitability of drone olfactory sensitivity as a selection trait for Varroa-resistance in honeybees

The most effective strategy against brood diseases, such as those stemming from infestation by the mite Varroa destructor, is the early detection and removal of sick brood. Recent findings suggest that genes associated with worker bee olfactory perception play a central role in Varroa-sensitive hygiene (VSH). In this study, the odour sensitivity of Apis mellifera drones was examined through proboscis extension response (PER) conditioning. Individuals sensitive/insensitive to the two Varroa-parasitised-brood odours (extract-low and extract-high) were used for breeding. Twenty-one queens from a VSH-selected line (SelQ) and nineteen queens from a nonselected line (ConQ) were single-drone-inseminated with sperm from drones that showed either sensitivity (SenD+) or insensitivity (SenD−) to the two extracts. Individual VSH behaviour in a total of 5072 offspring of these combinations (SelQ × SenD+, SelQ× SenD−, ConQ × SenD+, ConQ × SenD−) was subsequently observed in a specially designed observation unit with infrared light. The results from the video observation were also separately examined, considering the genetic origin (VSH-selected or nonselected line) of the participating queens and drones. While the drone PER conditioning results were not significantly reflected in the VSH results of the respective offspring, the genetic origin of the participating queens/drones was crucial for VSH manifestation.

Odours count: human olfactory ecology appears to be helpful in the improvement of the sense of smell

Odours modify human behaviour. Research in this field develops rapidly, providing more and more exciting discoveries. In this context, our daily odorous environment has been surprisingly poorly explored. The aim of our study was to quantify olfactory perception and preliminarily identify factors affecting the frequency of odorous experiences. We were also interested in knowing whether human olfactory ecology relates with olfactory performance. In this study, patients with olfactory deficits (n = 62) and healthy controls (n = 97) had their olfactory threshold and odour identification abilities measured before and after a two-week intervention comprising counting of conscious perception of odours naturally occurring in the environment. In both groups, we observed enhanced olfactory performance after the intervention suggesting that (1) the conscious focus on odours may change its perception, and that (2) social and physical environment can effectively stimulate the human olfactory system, presumably supporting the improvement of olfactory sensitivity.

The Circadian Clock, the Brain, and COVID-19: The Cases of Olfaction and the Timing of Sleep

Daily rhythms of behavior and neurophysiology are integral to the circadian clocks of all animals. Examples of circadian clock regulation in the human brain include daily rhythms in sleep-wake, cognitive function, olfactory sensitivity, and risk for ischemic stroke, all of which overlap with symptoms displayed by many COVID-19 patients. Motivated by the relatively unexplored, yet pervasive, overlap between circadian functions and COVID-19 neurological symptoms, this perspective piece uses daily variations in the sense of smell and the timing of sleep and wakefulness as illustrative examples. We propose that time-stamping clinical data and testing may expand and refine diagnosis and treatment of COVID-19.

Effect of Intranasal Administration of Dopamine on Odor Perception in Rats with Nigrostriatal Dysfunction

In recent years, there has been a growing interest in finding early predictors of Parkinson’s disease. In this regard, it is worth noting the olfactory dysfunction, which is associated with the death of neurons in the structures of the limbic system of the brain and a decrease in dopamine levels in the striatum. It was found that most patients with Parkinson’s disease have a clear olfactory dysfunction in the form of impaired differentiation and identification of odors. It has been suggested that the use of low doses of dopamine in the early stages of Parkinson’s disease will stop the progression of central nervous system disorders. The purpose of the study was to investigate the effect of intranasal administration of small doses of dopamine on the early manifestations of fine motor skills and olfactory sensory system function in nigrostriatal dysfunction in rats. Materials and methods. The experiments were performed on 2 groups of animals (n=14) with nigrostriatal dysfunction, which was modulated by partial bilateral electrical damage to the compact part of the substantia nigra. Stereotactic coordinates of the substantia nigra area were determined from the brain maps of rats by Fifkova and Marshall (quoted by Buresh), which corresponded to the distance from the point of intersection of the sagittal suture with bregma: F=5.5 mm, L=1.7 mm, H=9.0 mm. Rats of the first group (n=8) were intranasally administered with small doses of dopamine, and rats of the second group (n=6) were a comparison group. The fine motor skills of the forelimbs and the functional state of the olfactory system were studied when rats were presented with different odorants: emotionally positive (isovaleric acid) and emotionally negative (lemon essential oil) odorants. Results and discussion. The dynamics of the development of nigrostriatal dysfunction revealed a decrease in coordinated motor activity of the forelimbs, muscles of the oral pole and tongue and increased olfactory sensitivity to emotionally negative odorant (lemon essential oil) and loss of 40% of animals’ olfactory sensitivity to emotionally positive isovaleric odor. Conclusion. Prolonged intranasal administration of low doses of dopamine for 10 days to rats with nigrostriatal dysfunction resulted in a 26.2% increase in the activity of fine motor skills of the forelimbs, oral poles and tongue. In these rats, recovery of olfactory sensitivity to the perception of the smell of emotionally negative odorant was found. The action of the emotionally positive stimulus of isovaleric acid revealed an increase in olfactory sensitivity in 75% of animals to the level of baseline values and a decrease in the threshold of sensitivity to it, which was reflected in an increase in the number of approaches and time of odorant research